Combined effects of excess boron and salinity on the growth and ionic imbalance of lavandin (Lavandula × intermedia) plant

Generally, moderate to high salinity conditions and excess boron (B) occur together as limiting factors for plant growth in the soils of arid and semiarid regions. To determine the combined effect of excessive boron, salinity stress, or both, five different levels of B (0, 0.3, 0.6, 1.2, and 1.8 mM) and 80 mM sodium chloride (NaCl) were applied to lavandin plants grown in a greenhouse. The results showed that under nonsaline conditions, biomass production in shoots and roots and photosynthetic pigment contents (chlorophyll (Chl) a, b, and Chl a + b) decreased with exceptionally high B applications compared to the control. Moreover, the bioconcentration (BCF) of B (in shoots and roots), potassium (K) concentrations (in roots), K/sodium (Na) and calcium (Ca)/Na ratios (in shoots), and Ca/B ratios (in shoots and roots) decreased for all B applications compared to the control. In contrast, all B applications caused a remarkable increase in the carotenoid (Car)/Chl ratio, B concentrations (in shoots and roots), translocation (TF) of B, and net B accumulation compared to the control. In addition, under nonsaline conditions, concentrations of K (in shoots), Ca (in shoots and roots), and K/Na and Ca/Na ratios (in roots) were significantly increased by B applications compared with the control. Under saline conditions, significant decreases in Chl b, Chl a + b, BCF of B (in shoots and roots), and Ca/B ratio (in shoots) were observed in all B applications compared to the control. However, under saline conditions, B application caused significant increases in the Car/Chl ratio, TF of B, net B accumulation, and concentrations of B (in shoots and roots), K (in shoots), Ca, and Na (in shoots and roots) compared to the control. It was concluded that although it is not seen in the growth parameters, NaCl application could effectively alleviate the harmful effects of B toxicity in lavandin plants. Under saline conditions, notable decreases in the mean B concentration in shoots could be strong evidence for this hypothesis.